Bimodal hearing prosthesis

ABSTRACT

A bimodal hearing prosthesis for rehabilitating the hearing of a recipient. The hearing prosthesis comprises: a sound processing unit configured to process a received sound signal; and an implantable bimodal stimulation system, comprising: a mechanical stimulation arrangement configured to generate waves of fluid motion in a recipient&#39;s inner ear fluid based on the processed sound signal; an electrode assembly configured to deliver electrical stimulation signals generated based on the processed sound signal to a recipient&#39;s cochlea.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a National Stage Application of International Application No. PCT/US2009/038937, filed Mar. 31, 2009, and claims the benefit of U.S. Provisional Patent Application 61/041,185; filed Mar. 31, 2008. The contents of these applications are hereby incorporated by reference herein.

BACKGROUND

1. Field of the Invention

The present invention is generally directed to a hearing prosthesis, and more particularly, to a bimodal hearing prosthesis.

2. Related Art

Hearing loss, which may be due to many different causes, is generally of two types, conductive and sensorineural. In some cases, an individual may have hearing loss of both types. In many people who are profoundly deaf, however, the reason for their deafness is sensorineural hearing loss. Sensorineural hearing loss occurs when there is damage to the inner ear, or to the nerve pathways from the inner ear to the brain. As such, those suffering from sensorineural hearing loss are thus unable to derive suitable benefit from conventional acoustic hearing aids. As a result, hearing prostheses that deliver electrical stimulation to nerve cells of the recipient's auditory system have been developed to provide persons having sensorineural hearing loss with the ability to perceive sound. Such electrically-stimulating hearing prostheses deliver electrical stimulation to nerve cells of the recipient's auditory system.

As used herein, the recipient's auditory system includes all sensory system components used to perceive a sound signal, such as hearing sensation receptors, neural pathways, including the auditory nerve and spiral ganglion, and parts of the brain used to sense sounds. Electrically-stimulating hearing prostheses include, for example, auditory brain stimulators and cochlear™ prostheses (commonly referred to as cochlear prosthetic devices, cochlear implants, cochlear devices, and the like; simply “cochlear implants” herein.)

Most sensorineural hearing loss is due to the absence or destruction of the cochlea hair cells which transduce acoustic signals into nerve impulses. It is for this purpose that cochlear implants have been developed. Cochlear implants electrically stimulate a recipient's cochlea by directly delivering direct electrical stimulation signals to the auditory nerve cells, thereby bypassing absent or defective hair cells that normally transduce acoustic vibrations into neural activity. Such devices generally use an electrode array implanted in the cochlea so that the electrodes may differentially activate auditory neurons that normally encode differential pitches of sound.

In contrast to sensorineural hearing loss, conductive hearing loss occurs when the normal mechanical pathways used to provide sound to hair cells in the cochlea are impeded, for example, by damage to the ossicular chain or to the ear canal. Individuals who suffer from conductive hearing loss typically have some form of residual hearing because the hair cells in the cochlea are undamaged. As a result, individuals suffering from conductive hearing loss typically receive an acoustic hearing aid. Acoustic hearing aids stimulate an individual's cochlea by providing an amplified sound to the cochlea, where the amplified sound causes mechanical motion of the cochlear fluid.

Unfortunately, not all individuals who suffer from conductive hearing loss are able to derive suitable benefit from hearing aids. For example, some individuals are prone to chronic inflammation or infection of the ear canal and cannot wear hearing aids. Similarly, hearing aids are typically unsuitable for individuals who have malformed, damaged or absent outer ears, ear canals and/or ossicular chains.

SUMMARY

In one aspect of the invention, a bimodal hearing prosthesis for rehabilitating the hearing of a recipient is provided. The hearing prosthesis comprises: a sound processing unit configured to process a received sound signal; and an implantable bimodal stimulation system, comprising: a mechanical stimulation arrangement configured to generate waves motion in a recipient's inner ear fluid based on the processed sound signal; an electrode assembly configured to deliver to the recipient's cochlea electrical stimulation signals generated based on the processed sound signal.

In another aspect of the invention, a method for rehabilitating the hearing of a recipient with a bimodal hearing prosthesis comprising an implantable electrode assembly configured to electrically stimulate a recipient and an implantable mechanical stimulation arrangement configured to directly mechanically stimulate the recipient's inner ear by generating waves of fluid motion in the recipient's inner ear fluid is provided. The method comprises: receiving an acoustic sound signal; processing the acoustic sound signal; generating one or more of electrical stimulation signals and mechanical stimulation signals, based on the processed acoustic sound signal; and stimulating the recipient's inner ear using the generated stimulation signals.

In a still other aspect of the present invention, a bimodal hearing prosthesis for rehabilitating the hearing of a recipient is provided. The prosthesis comprises: means for receiving an acoustic sound signal; means for processing the acoustic sound signal; means for generating one or more of electrical stimulation signals and mechanical stimulation signals, based on the processed acoustic sound signal; and means for stimulating the recipient's inner ear based on the generated stimulation signals

BRIEF DESCRIPTION OF THE DRAWINGS

Illustrative embodiments of the present invention are described herein with reference to the accompanying drawings, in which:

FIG. 1A is a partial cross-sectional view of an individual's head in which embodiments of the present invention may be implemented;

FIG. 1B is a perspective, partially cut-away view of a cochlea exposing the canals and nerve fibers of the cochlea;

FIG. 1C is a cross-sectional view of one turn of the canals of a human cochlea;

FIG. 2 is a perspective view of an implanted bimodal hearing prosthesis in accordance with embodiments of the present invention;

FIG. 3 is a functional block diagram of a bimodal hearing prosthesis in accordance with embodiments of the present invention;

FIG. 4 is a perspective view of a mechanical stimulation arrangement, in accordance with embodiments of the present invention;

FIG. 5 is a perspective view of a mechanical stimulation arrangement, in accordance with embodiments of the present invention;

FIG. 6 is a simplified side view of cochlea having an electrode assembly in accordance with embodiments of the present invention implanted therein; and

FIG. 7 is flowchart illustrating the operations performed by a bimodal hearing prosthesis.

DETAILED DESCRIPTION

Aspects of the present invention are generally directed to a hearing prosthesis configured to selectively electrically and/or mechanically stimulate a recipient's cochlea. Such a hearing prosthesis, referred to herein as a bimodal hearing prosthesis, comprises an electrode assembly configured to be implanted in a recipient's cochlea, and a mechanical stimulation arrangement. The electrode assembly delivers electrical stimulation signals to the cochlea, while the mechanical stimulation arrangement bypasses the recipient's outer and middle ears to directly generate waves of fluid motion in the recipient's inner ear. In certain embodiments, the mechanical stimulation arrangement is configured to be positioned adjacent the inner ear and may comprise, for example, a middle ear or inner ear mechanical stimulator. In other embodiments, the mechanical stimulation arrangement is a bone conduction device.

FIG. 1A is perspective view of an individual's head 100 in which embodiments of a bimodal hearing prosthesis in accordance with embodiments of the present invention may be implemented. As shown in FIG. 1A, the individual's hearing system comprises an outer ear 101, a middle ear 105 and an inner ear 107. In a fully functional ear, outer ear 101 comprises an auricle 110 and an ear canal 102. An acoustic pressure or sound wave 103 is collected by auricle 110 and channeled into and through ear canal 102. Disposed across the distal end of ear cannel 102 is a tympanic membrane 104 which vibrates in response to sound wave 103. This vibration is coupled to oval window or fenestra ovalis 112 through three bones of middle ear 105, collectively referred to as the ossicles 106 and comprising the malleus 108, the incus 109 and the stapes 111. Bones 108, 109 and 111 of middle ear 105 are disposed within mastoid bone 119 and serve to filter and amplify sound wave 103, causing oval window 112 to articulate, or vibrate in response to vibration of tympanic membrane 104. This vibration sets up waves of fluid motion of the perilymph within cochlea 140. Such fluid motion, in turn, activates tiny hair cells (not shown) inside of cochlea 140. Activation of the hair cells causes appropriate nerve impulses to be generated and transferred through the spiral ganglion cells (not shown) and auditory nerve 114 to the brain (also not shown) where they are perceived as sound.

Also shown in FIG. 1A are semicircular canals 125. Semicircular canals 125 are three half-circular, interconnected tubes located adjacent cochlea 140. The three canals are the horizontal semicircular canal 126, the posterior semicircular canal 127, and the superior semicircular canal 128, all of which are aligned approximately orthogonally to one another. Specifically, horizontal canal 126 is aligned roughly horizontally in the head, while the superior 128 and posterior canals 127 are aligned roughly at a 45 degree angle to a vertical through the center of the individual's head 100.

Each of the semicircular canals 125 is filled with a fluid known as endolymph, and contains a tiny hairs (not shown) whose ends are embedded in a gelatinous structure known as the cupula (also not shown). As the individual's head 100 twists in various directions, the endolymph moves into different sections of semicircular canals 125. The hairs detect when the endolymph passes thereby, and a signal is then sent to the brain. Therefore, using the hair cells, horizontal canal 126 is able to detect horizontal head movements, while the superior 128 and posterior 127 canals are able to detect vertical head movements.

The details of cochlea 140 are described next below with reference to FIGS. 1B and 1C. FIG. 1B is a perspective view of cochlea 140 partially cut-away to display the canals and nerve fibers of the cochlea, while FIG. 1C is a cross-sectional view of one turn of the canals of cochlea 140.

Referring to FIG. 1B, cochlea 140 is a conical spiral structure comprising three parallel fluid-filled canals or ducts, collectively and generally referred to herein as canals 132. Canals 132 comprise the tympanic canal 138, also referred to as the scala tympani 138, the vestibular canal 134, also referred to as the scala vestibuli 134, and the median canal 136, also referred to as the cochlear duct 136. Cochlea 140 has a conical shaped central axis, the modiolus 154, that forms the inner wall of scala vestibuli 134 and scala tympani 138. The base of scala vestibuli 134 comprises oval window 112 (FIG. 1A), while the base of scala tympani 138 terminates in round window 121 (FIG. 1A). Tympanic and vestibular canals 138, 134 transmit pressure waves received at oval window 112, while medial canal 136 contains the organ of Corti 150 which detects pressure impulses and responds with electrical impulses which travel along auditory nerve 114 to the brain (not shown).

Cochlea 140 spirals about modiolus 154 several times and terminates at cochlea apex 146. Modiolus 154 is largest near its base where it corresponds to first turn 151 of cochlea 140. The size of modiolus 154 decreases in the regions corresponding to medial 152 and apical turns 156 of cochlea 140.

Referring now to FIG. 1C, separating canals 132 of cochlear 140 are various membranes and other tissue. The ossicous spiral lamina 182 projects from modiolus 154 to separate scala vestibuli 134 from scala tympani 138. Toward lateral side 172 of scala tympani 138, a basilar membrane 158 separates scala tympani 138 from cochlear duct 136. Similarly, toward lateral side 172 of scala vestibuli 134, a vestibular membrane 166, also referred to as the Reissner's membrane 166, separates scala vestibuli 134 from cochlear duct 136.

Portions of cochlea 140 are encased in a bony capsule 170. Bony capsule 170 resides on lateral side 172 (the right side as drawn in FIG. 1C), of cochlea 140. Spiral ganglion cells 180 reside on the opposing medial side 174 (the left side as drawn in FIG. 1C) of cochlea 140. A spiral ligament membrane 164 is located between lateral side 172 of spiral tympani 138 and bony capsule 170, and between lateral side 172 of cochlear duct 136 and bony capsule 170. Spiral ligament 164 also typically extends around at least a portion of lateral side 172 of scala vestibuli 134.

Sound entering auricle 110 causes pressure changes in cochlea 140 to travel through the fluid-filled tympanic and vestibular canals 138, 134. As noted, organ of Corti 150 is situated on basilar membrane 158 in cochlear duct 136. It contains rows of 16,000-20,000 hair cells (not shown) which protrude from its surface. Above them is the tectoral membrane 162 which moves in response to pressure variations in the fluid-filled tympanic and vestibular canals 138, 134. Small relative movements of the layers of membrane 162 are sufficient to cause the hair cells to send a voltage pulse or action potential down the associated nerve fiber 178. Nerve fibers 178, embedded within spiral lamina 182, connect the hair cells with the spiral ganglion cells 180 which form auditory nerve 114. Auditory nerve 114 relays the impulses to the auditory areas of the brain (not shown) for processing.

The place along basilar membrane 158 where maximum excitation of the hair cells occurs determines the perception of pitch and loudness according to the place theory. Due to this anatomical arrangement, cochlea 140 has characteristically been referred to as being “tonotopically mapped.” That is, regions of cochlea 140 toward basal region 116 (FIG. 1) are responsive to high frequency signals, while regions of cochlea 140 toward apex 146 are responsive to low frequency signals. As discussed in greater detail below, these tonotopical properties of cochlea 140 are exploited in a cochlear implant by delivering stimulation signals within a predetermined frequency range to a region of the cochlea that is most sensitive to that frequency range.

The fluid in tympanic and vestibular canals 138, 134, referred to as perilymph, has different properties than that of the fluid which fills cochlear duct 136 and which surrounds organ of Corti 150, referred to as endolymph. As described above with reference to FIG. 1A, semicircular canals 125 are also filled with endolymph. The vestibule 129 (FIG. 1A) provides fluid communication between the endolymph in semicircular canals 125 and the endolymph in cochlear duct 136.

FIG. 2 is a perspective view of bimodal hearing prosthesis 200 in accordance with embodiments of the present invention. Bimodal hearing prosthesis 200 comprises an external component 242 which is directly or indirectly attached to the body of the recipient, and an internal component 244 which is temporarily or permanently implanted in the recipient. External component 242 typically comprises one or more sound input elements, such as microphone 224 for detecting sound, a sound processing unit 226, a power source (not shown), and an external transmitter unit 228. External transmitter unit 228 comprises an external coil 230 and, preferably, a magnet (not shown) secured directly or indirectly to external coil 230. Sound processing unit 226 processes the output of microphone 224 that is positioned, in the depicted embodiment, by auricle 110 of the recipient. Sound processing unit 226 generates encoded signals, sometimes referred to herein as encoded data signals, which are provided to external transmitter unit 228 via a cable (not shown).

Internal component 244 comprises an internal receiver unit 232, a stimulator unit 220, and a bimodal stimulation system 280. Bimodal stimulation system 280 comprises an elongate electrode assembly 248 and a mechanical stimulation arrangement 215. Internal receiver unit 232 comprises an internal coil 236, and preferably, a magnet (also not shown) fixed relative to the internal coil. Internal receiver unit 232 and stimulator unit 220 are hermetically sealed within a biocompatible housing, sometimes collectively referred to as a stimulator/receiver unit.

In the illustrative embodiment of FIG. 2, external coil 230 transmits electrical signals (i.e., power and stimulation data) to internal coil 236 via a radio frequency (RF) link. Internal coil 236 is typically a wire antenna coil comprised of multiple turns of electrically insulated single-strand or multi-strand platinum or gold wire. The electrical insulation of internal coil 236 is provided by a flexible silicone molding (not shown). In use, implantable receiver unit 232 may be positioned in a recess of the temporal bone adjacent auricle 110 of the recipient.

As noted, internal component 244 further includes a bimodal stimulation system 280. As shown, bimodal stimulation system 280 comprises an electrode assembly 248 which is configured to be implanted in cochlea 140. Electrode assembly 248 comprises a longitudinally aligned and distally extending array 245 of electrodes 246, sometimes referred to as electrode array 245 herein, disposed along a length thereof. Although electrode array 245 may be disposed on electrode assembly 248, in most practical applications, electrode array 245 is integrated into electrode assembly 248. As such, electrode array 245 is referred to herein as being disposed in electrode assembly 248. The proximal end of electrode assembly 248 is electrically connected to a lead 262 extending from stimulator unit 220. As described below, in embodiments of the present invention, stimulator unit 220 generates, based on data signals received at receiver unit 232, electrical stimulation signals which are delivered to electrode assembly 248 via lead 262. The stimulation signals are applied by electrodes 246 to cochlea 140, thereby stimulating auditory nerve 114.

As described in greater detail below, in embodiments of the present invention, electrode assembly 248 is implanted at least in basal region 116 of cochlea 140, and sometimes further. For example, electrode assembly 248 may extend towards apical end of cochlea 140, referred to as cochlea apex 134. In certain circumstances, electrode assembly 248 may be inserted into cochlea 140 via a cochleostomy 122. In other circumstances, a cochleostomy may be formed through round window 121, oval window 112 (FIG. 1A), the promontory 123 or through an apical turn 147 of cochlea 140.

Electrode assembly 248 may comprise a perimodiolar electrode assembly which is configured to adopt a curved configuration during and or after implantation into the recipient's cochlea. In one such embodiment, electrode assembly 248 is pre-curved to the same general curvature of a cochlea. Electrode assembly 248 is held straight by, for example, a stiffening stylet (not shown) which is removed during implantation so that the assembly adopts the curved configuration. Other methods of implantation, as well as other electrode assemblies which adopt a curved configuration may be used in alternative embodiments of the present invention.

In other embodiments, electrode assembly 248 comprises a non-perimodiolar electrode assembly which does not adopt a curved configuration. For example, electrode assembly 248 may comprise a straight assembly or a mid-scala assembly which assumes a mid-scala position during or following implantation.

As shown in FIG. 2, bimodal stimulation system 280 further comprises mechanical stimulation arrangement 215. As previously noted, a mechanical stimulation arrangement in accordance with embodiments of the present invention may comprise a middle ear or inner ear mechanical stimulator, or a bone conduction device. Details of exemplary bone conduction devices that may utilized with embodiments of the present invention are described in U.S. Provisional Patent Application 61/041,185. For ease of illustration, embodiments of the present invention will be described with reference to a mechanical stimulation arrangement that stimulates the recipient's inner ear. However, this exemplary illustration should not be considered to limit the present invention.

In the illustrative embodiment of FIG. 2, ossicles 106 have been omitted from FIG. 2 to illustrate an exemplary location of the inner ear mechanical stimulation arrangement 215. It should be appreciated that stimulation arrangement 215 may be implanted without disturbing ossicles 106.

Stimulation arrangement 215 comprises an actuator 240 electrically connected to stimulator unit 220 by lead 264, a stapes prosthesis 254 and a coupling element 253. As described in greater detail below with reference to FIG. 5, in this illustrative embodiment, coupling element 253 connects actuator 240 to stapes prosthesis 254 which abuts round window 121 (FIG. 1A). In certain embodiments of the present invention, based on data signals received at receiver unit 232, stimulator unit 220 generates actuator drive signals which cause vibration of actuator 240. This vibration is transferred to the inner ear fluid (perilymph) in the recipient's scala tympani via coupling element 253 and stapes prosthesis 254, thereby evoking a hearing percept by the recipient.

Although the embodiments of FIG. 2 have been described with reference to a bimodal hearing prosthesis 200 having an external component, it should be appreciated that in alternative embodiments bimodal hearing prosthesis 200 is a totally implantable device. In such embodiments, sound processing unit 226 is implanted in a recipient in the mastoid bone and the sound processing unit communicates directly with stimulator unit 220, thereby eliminating the need for transmitter unit 228 and receiver unit 232.

FIG. 3 is a functional block diagram illustrating an embodiment of bimodal hearing prosthesis 200, referred to herein as bimodal hearing prosthesis 300. In the illustrated embodiment, bimodal hearing prosthesis 300 comprises an external component 342, and an internal component 344. External component 342 comprises one or more sound input elements 324 for detecting sound, a sound processing unit 326, a power source (not shown), and an external transmitter unit 328.

Sound input element 324 receives a sound signal 301 and generates an electrical output signal 303 representing the sound. Electrical signal 303 is provided to sound processing unit 326 which converts the signal into encoded data signals which may be transmitted to internal component 344. More specifically, in the illustrative embodiment of FIG. 3, electrical signal 303 is provided to a preprocessor 350. In embodiments of the present invention, preprocessor 350 filters signal 303 and provides a signal component 305 in a first frequency band to an electrical stimulation processor 352, and provides a signal component 307 in a second frequency band to a mechanical stimulation processor 354. The first frequency band comprises a high frequency portion of the audible frequency spectrum, which, as described above, is perceivable by the basal region of a cochlea. The second frequency band comprises a low frequency portion of the audible frequency spectrum, which is perceivable by apical regions of a cochlea. In other words, in the illustrative embodiments of FIG. 3, preprocessor 350 performs a frequency analysis of sound 301 and/or signal 303, and allocates certain frequency portions to signals 305 and 307.

Electrical stimulation processor 352 processes signal component 305 to generate a processed electrical signal 309 representing the high frequency components of sound signal 301. Similarly, mechanical stimulation processor 354 processes signal component 307 to generate a processed electrical signal 311 representing the low frequency components of sound signal 301. Signals 309, 311 are then provided to transmitter unit 328 where the signals are encoded and transmitted to receiver unit 332 in internal component 344. Internal receiver unit decodes the transmitted signals, and provides electrical signals 309, 311 to stimulator unit 320.

Based on electrical signals 309, 311, stimulator unit 320 generates stimulation signals which are provided to one or more components of bimodal stimulation system 380. As shown, bimodal stimulation system 380 comprises an electrode assembly 318 and a mechanical stimulation arrangement 315. Stimulator unit 320 comprises an electrical stimulation signal generator 356 configured to generate electrical stimulation signals 319 based on electrical signals 309. Electrical stimulation signals 319 are provided to electrode assembly 318 for delivery to the recipient, thereby stimulating auditory nerve 114 (FIG. 1).

Stimulator unit 320 further comprises actuator drive components 358. Based on signal 311, actuator drive components 358 generate stimulation signals 321 which are provided to mechanical stimulation arrangement 315. Stimulation signals 321, sometimes referred to herein as actuator drive signals 321, cause vibration of an actuator within mechanical stimulation arrangement 315. As described above, in certain embodiments the actuator is coupled to the recipient's inner ear, the vibration is transferred to the inner ear fluid, thereby evoking a hearing percept by the recipient. In other embodiments, the actuator is a positioned to deliver vibration to the recipient's skull. For example, the actuator may be part of an externally worn bone conduction device, or an implanted bone conduction device.

Although the embodiments of FIG. 3 have been described with reference to a bimodal hearing prosthesis 300 having an external component, it should be appreciated that in alternative embodiments bimodal hearing prosthesis 300 is a totally implantable device. In such embodiments, sound processing unit 326 is implanted in a recipient in the mastoid bone and the sound processing unit communicates directly with stimulator unit 320, thereby eliminating the need for transmitter unit 328 and receiver unit 332.

Similarly, bimodal hearing prosthesis 300 has been described above with reference to a preprocessor 350 which filters electrical signal 303 based on the frequency of received sound signal 301. It should be appreciated that preprocessor 350 may also filter electrical signal 303 using alternative criteria, signal characteristics, etc. For example, in certain embodiments, preprocessor 350 may allocate the entirety of electrical signal 303 to electrical stimulation processor 352 or mechanical stimulation processor 354.

FIG. 4 illustrates an exemplary mechanical stimulation arrangement 415 which may be implemented in a bimodal hearing prosthesis in accordance with embodiments of the present invention. As previously noted, mechanical stimulation arrangement may comprise a middle ear or inner ear stimulator, or a bone conduction device. In the illustrative embodiment of FIG. 4, stimulation arrangement 415 is a inner ear stimulator configured to generate wave(s) of fluid motion of the endolymph contained in a recipient's semicircular canal 126. Because, as noted above, vestibule 129 (FIG. 1A) provides fluid communication between the semicircular canal 126 and the cochlear duct 136 (FIG. 1B), a generated wave of fluid motion continues into cochlear duct 136, thereby activating the hair cells of the organ of Corti 150 (FIG. 1C). Activation of the hair cells causes appropriate nerve impulses to be generated and transferred through the spiral ganglion cells (FIG. 1C) and auditory nerve (FIG. 1A) to the recipient's brain where they are perceived as sound.

Stimulation arrangement 415 comprises an actuator 440 coupled to a stimulator unit (not shown) by a lead or cable 428. Actuator 440 may be positioned and secured to the recipient by a fixation system. Exemplary fixation systems that may be used to secure actuator 440 to the recipient are described in commonly owned and co-pending U.S. patent application Ser. No. 12/349,495 entitled “MECHANICAL SEMICIRCULAR CANAL STIMULATOR,” and commonly owned and co-pending U.S. patent application Ser. No. 12/349,502 entitled “MECHANICAL SCALA TYMPANI CANAL STIMULATOR,” the contents of both are hereby incorporated by reference herein in their entirety.

In the embodiments of FIG. 4, stimulation arrangement 415 comprises a stapes prosthesis 452. Stapes prosthesis 452 is a substantially cylindrical member having a first end 460 abutting an opening 405 in the recipient's horizontal semicircular canal 126. Connecting actuator 440 and stapes prosthesis 452 is a coupler 409. Coupler 409 comprises a first elongate component 404 extending longitudinally from actuator 440. Disposed at the distal portion of first component 404 is a second component 406. Second component is oriented such that the component extends away first component 404 at an angle and connects to stapes prosthesis 452. In other words, an axis 411 extending through the center of second component 406 along the direction of orientation is at an angle from the longitudinal axis 407 of first component 404. In certain embodiments, second component 406 is oriented such that axis 411 is positioned at an angle of approximately 125 degrees from longitudinal axis 407.

To implant stimulation arrangement 415, a surgeon may drill or form a passageway in the mastoid of the skull. This passageway is preferably constructed and arranged such that it provides direct access to the cochlea. In this embodiment, the surgeon then drills or forms an opening in one of the recipient's semicircular canals 125 (FIG. 1). In the illustrative embodiment of FIG. 4, this opening is created in horizontal semicircular canal 126, however it would be appreciated that an opening created in posterior semicircular canal 127 (FIG. 1A) or superior semicircular canal 128 (FIG. 1A) may also be used.

FIG. 5 illustrates an alternative stimulation arrangement 515 which may be implemented in a bimodal hearing prosthesis in accordance with embodiments of the present invention. In the illustrative embodiment of FIG. 5, stimulation arrangement 515 is configured to generate fluid motion of the perilymph contained in a recipient's scala tympani 138 (FIG. 1B). As discussed above, fluid motion of the perilymph activates the hair cells of the organ of Corti 150 (FIG. 1C). Activation of the hair cells causes appropriate nerve impulses to be generated and transferred through the spiral ganglion cells (FIG. 1C) and auditory nerve (FIG. 1A) to the recipient's brain where they are perceived as sound.

Stimulation arrangement 515 comprises an actuator 540 coupled to a stimulator unit (not shown) by a lead or cable (not shown). Actuator 540 may be positioned and secured to the recipient by a fixation system. Exemplary fixation systems that may be used to secure actuator 540 to the recipient are described in commonly owned and co-pending U.S. patent application Ser. No. 12/349,495 entitled “MECHANICAL SEMICIRCULAR CANAL STIMULATOR,” and commonly owned and co-pending U.S. patent application Ser. No. 12/349,502 entitled “MECHANICAL SCALA TYMPANI CANAL STIMULATOR,” the contents of both are hereby incorporated by reference herein in their entirety.

Stimulation arrangement 515 further comprises a stapes prosthesis 554. As shown in FIG. 5, stapes prosthesis 554 is a substantially cylindrical member having a first end 560 and a second end 514. As shown, first and second ends 560 and 514 have cross-sectional diameters which exceed the cross-sectional diameter of the remainder of prosthesis 554. Distal end 560 is configured to be positioned abutting the membrane of round window 121 in the recipient's cochlea.

Connecting actuator 540 and stapes prosthesis 554 is a coupler 509. In the illustrative embodiment, coupler 509 comprises an elongate rod extending longitudinally from actuator 540 along axis 507. The distal portion of rod 508 is connected to stapes prosthesis 554. In the illustrative embodiment of FIG. 5A, stapes prosthesis 554 is aligned along, and is substantially symmetrical about axis 507. In other words, the surface of first end 560 is positioned orthogonal to axis 507. As described in commonly owned and co-pending U.S. patent application Ser. No. 12/349,502 entitled “MECHANICAL SCALA TYMPANI CANAL STIMULATOR,” various embodiments of coupler 509 are possible. Similarly, various different mechanisms may be used to connect coupler 509 to stapes prosthesis 554.

FIGS. 4 and 5 illustrate embodiments of mechanical stimulation arrangements 415, 515, which may be implemented in a bimodal hearing prosthesis in accordance with embodiments of the present invention. Further features of stimulation arrangements which may be implemented in embodiments of the present invention are described in commonly owned and co-pending U.S. patent application Ser. No. 12/349,495 entitled “MECHANICAL SEMICIRCULAR CANAL STIMULATOR,” and commonly owned and co-pending U.S. patent application Ser. No. 12/349,502 entitled “MECHANICAL SCALA TYMPANI CANAL STIMULATOR,” the contents of both are hereby incorporated by reference herein in their entirety.

As noted above, various electrode assemblies may be used in embodiments of the present invention. For example, in embodiments of the present invention an electrode assembly may be implanted in basal region 116 (FIG. 1) of cochlea 140 (FIG. 1), or the electrode assembly may extend towards apical end of cochlea 140, referred to as cochlea apex 134. FIG. 6 is a simplified side view of a recipient's cochlea 140 having implanted therein an electrode assembly 646 utilized in embodiments of the present invention. In the illustrative embodiment of FIG. 6, electrode assembly 646 is implanted only in the basal region of cochlea 140. Such an electrode assembly is sometimes referred to herein as a short electrode assembly. For ease of illustration, a simplified view of cochlea 140 is shown. As such, the scala tympani and the scala vestibule have not been differentiated in FIG. 6. It would be appreciated that short electrode assembly 646 may be inserted into either the scala tympani or the scala vestibuli of cochlea 140.

As noted above, cochlea 140 is “tonotopically mapped.” That is, regions of cochlea 140 in basal region 116 are responsive to high frequency signals, while regions of cochlea 140 toward apex 146 are responsive to low frequency signals. As a result of this tonotopic arrangement, individuals may suffer sensorineural hearing loss only in certain frequency ranges. For example, certain individuals may loss the ability to perceive high frequency signals (ie. suffer sensorineual hearing loss in the basal regions of the cochlea), while retaining the ability to perceive low frequency signals. Such individuals maintain the ability to perceive middle to lower frequency sounds naturally, but have limited or no ability to perceive high frequency sounds. Short electrode assembly 646 of FIG. 6 may be advantageously implemented in such individuals.

In the embodiment of FIG. 6, when short electrode assembly 646 is fully implanted, distal end 636 of the electrode assembly is positioned at or near distal end 639 of basal region 116. As used herein, basal region 116 of cochlea 140 is the portion of the scala tympani and the scala vestibuli extending from the round window and oval window, respectively, to the first turn 641 of cochlea 140. Therefore, when short electrode assembly 646 is fully implanted in cochlea 140, distal end 636 of the short electrode assembly is positioned at, in, or proximate to the region of cochlea 140 at which the first turn 641 of cochlea 140 begins. As used herein, the positioning of distal end 636 in this region of cochlea 140 includes positioning the distal end in basal region 116 or in first turn 641.

As shown, short electrode assembly 646 includes an array of electrodes 648. Electrodes 648 are configured to apply electrical stimulation signals (not shown) to basal region 116 of cochlea 140. In certain embodiments, electrode assembly 646 comprises a perimodiolar electrode assembly configured to adopt a curved configuration during and or after implantation into the recipient's cochlea. In one such embodiment, distal portion 618 of electrode assembly 646 is pre-curved so as to be positioned in first turn 641. Electrode assembly 646 is held straight by, for example, a stiffening stylet (not shown) which is removed during implantation so that distal end 636 adopts the curved configuration. Other methods of implantation, as well as other electrode assemblies which adopt a curved configuration may be used in alternative embodiments of the present invention. In other embodiments, electrode assembly 646 comprises a non-perimodiolar electrode assembly which does not adopt a curved configuration.

Although the embodiments of FIG. 6 have been described with reference to a short electrode assembly 646, it should be appreciated that other electrode assemblies may be implemented in certain embodiments of the present invention. For example, in some embodiments, an electrode assembly that extends into medial region 643 and or apical region 645 may be used.

FIG. 7 is a flowchart illustrating the operations performed in a method 700 implemented by a bimodal hearing prosthesis in accordance with embodiments of the present invention. During the implemented method, a sound signal is received at block 702, by, for example, a sound input element such as a microphone, telecoil, electrical input, etc.

As previously noted, a bimodal hearing prosthesis in accordance with embodiments of the present invention may be configured to electrically and/or mechanically stimulate a recipient's cochlea. As such, at block 704, the bimodal hearing prosthesis selects which of these mode or modes of stimulation will be used to stimulate the recipient's cochlea. At block 706 the bimodal hearing prosthesis generates stimulation signals in accordance with the modes selected at block 704. At block 708, the recipient's inner ear is stimulated using the stimulation signals.

The invention described and claimed herein is not to be limited in scope by the specific preferred embodiments herein disclosed, since these embodiments are intended as illustrations, and not limitations, of several aspects of the invention. Any equivalent embodiments are intended to be within the scope of this invention. 

1. A bimodal hearing prosthesis for rehabilitating the hearing of a recipient, comprising: a sound processing unit configured to process a received sound signal; and an implantable bimodal stimulation system, comprising: a mechanical stimulation arrangement configured to generate waves of fluid motion in the recipient's inner ear fluid based on the processed sound signal; an electrode assembly configured to deliver to the recipient's cochlea electrical stimulation signals generated based on the processed sound signal.
 2. The prosthesis of claim 1, wherein the mechanical stimulation arrangement comprises: a stapes prosthesis having a first end configured to be positioned so as to abut an opening in one of the recipient's semicircular canals; an actuator configured to receive electrical signals representing the processed sound configured to vibrate in response to the electrical signals; and a coupler connecting the actuator to the stapes prosthesis such that vibration of the actuator results in the direct generation of waves of fluid motion in the semicircular canal.
 3. The prosthesis of claim 1, wherein the mechanical stimulation arrangement comprises: an actuator configured to receive electrical signals representing the processed sound signal and configured to vibrate in response to the electrical signals; a stapes prosthesis having first and second ends, the first end having a surface configured to be positioned abutting the round window in the recipient's cochlea, and wherein the first end surface is substantially orthogonal to a longitudinal axis extending through the actuator; and an elongate rod connecting the actuator to the stapes prosthesis such that vibration of the actuator results in the direction generation of waves of fluid motion in the recipient's scala tympani.
 4. The prosthesis of claim 2, wherein the coupler comprises: a first elongate component extending longitudinally from the actuator, and a second component attached to, and extending from the distal portion of the first component at an angle.
 5. The prosthesis of claim 2, wherein the first elongate component comprises: an elongate rod having an adjustable length.
 6. The prosthesis of claim 4, wherein the second component is attached to the first component by a pivot joint configured to permit adjustment of the angle at which the second component extends from the first component.
 7. The prosthesis of claim 1, wherein the mechanical stimulation arrangement comprises an actuator configured to vibrate the recipient's skull. 8-14. (canceled)
 15. The prosthesis of claim 1, further comprising: a preprocessor configured to evaluate the processed sound signal and to select which one or more of the mechanical stimulation arrangement and the electrode assembly is to be used to stimulate the recipient's cochlea based on the processed sound signal.
 16. The prosthesis of claim 15, wherein the preprocessor is configured to perform a frequency analysis of the received sound signal to select which one or more of the mechanical stimulation arrangement and the electrode assembly is to be used to stimulate the recipient's cochlea
 17. A method for rehabilitating the hearing of a recipient with a bimodal hearing prosthesis the prosthesis comprising an implantable electrode assembly configured to electrically stimulate a recipient and an implantable mechanical stimulation arrangement configured to mechanically stimulate the recipient's inner ear by generating waves of fluid motion in the recipient's inner ear fluid, the method comprising: receiving an acoustic sound signal; processing the acoustic sound signal; generating one or more of electrical stimulation signals and mechanical stimulation signals, based on the processed acoustic sound signal; and stimulating the recipient's inner ear based on the generated stimulation signals.
 18. The method of claim 17, wherein generating one or more of electrical stimulation signals and mechanical stimulation signals, comprises: generating electrical stimulation signals, and simultaneously generating mechanical stimulation signals.
 19. The method of claim 17, further comprising: directly generating waves of fluid motion in one of the recipient's semicircular canals.
 20. The method of 17, further comprising: directly generating waves of fluid motion in the recipient's scala tympani.
 21. The method of claim 19, wherein the mechanical stimulation arrangement comprises a stapes prosthesis having a first end configured to be positioned abutting an opening in the semicircular canal, an actuator and a coupler connecting the actuator to the stapes prosthesis, wherein generating the fluid motion comprises: receiving at the actuator electrical signals representing the processed sound signals; generating vibration with the actuator based on the electrical signals; and delivering the vibration to the fluid in the semicircular canal with the stapes prosthesis.
 22. The method of claim 21, wherein the coupler comprises a first elongate component extending from the actuator, and a second component extending from the distal portion of the first component at an angle, wherein delivering the vibration to the fluid in the semicircular canal with the stapes prosthesis comprises: actuating the first component to exert a force on the fluid in the semicircular canal.
 23. The method of 17, further comprising: delivering the mechanical stimulation signals to an actuator configured to generate vibration of the recipient's skull.
 24. The method of claim 20, wherein the mechanical stimulation arrangement comprises a stapes prosthesis having a first end configured to be positioned abutting the round window in a recipient's cochlea, an actuator, and an elongate rod connecting the actuator to the stapes prosthesis, wherein generating the fluid motion further comprises: receiving at the actuator electrical signals representing the processed sound signals; generating vibration with the actuator based on the electrical signals; and delivering with the stapes prosthesis the vibration to round window.
 25. (canceled)
 26. The method of claim 17, further comprising: performing a frequency analysis of the received sound signal. 27-32. (canceled)
 33. A bimodal hearing prosthesis for rehabilitating the hearing of a recipient, comprising: means for receiving an acoustic sound signal; means for processing the acoustic sound signal; means for generating one or more of electrical stimulation signals and mechanical stimulation signals, based on the processed acoustic sound signal; and means for stimulating the recipient's inner ear based on the generated stimulation signals.
 34. The prosthesis of claim 33, wherein generating one or more of electrical stimulation signals and mechanical stimulation signals, comprises: means for generating electrical stimulation signals, and means for simultaneously generating mechanical stimulation signals.
 35. The prosthesis of claim 33, further comprising: means for directly generating fluid motion in one of the recipient's semicircular canals.
 36. The prosthesis of claim 33, further comprising: means for directly generating fluid motion in the recipient's scala tympani.
 37. The prosthesis of claim 33, further comprising: means for delivering the mechanical stimulation signals to an actuator configured to generate vibration of the recipient's skull.
 38. The prosthesis of claim 33, further comprising: means for performing a frequency analysis of the received sound signal. 